Ivory Coast ? Protesters defied a call by Ivory Coast’s president to end street violence that entered its fourth day Thursday, as the U.N. Security Council warned of possible sanctions against those trying to sabotage the African nation’s peace process.

U.N. peacekeepers fired tear-gas grenades to keep back hundreds of angry young men protesting outside U.N. headquarters in Abidjan, the country’s main city.

Shops, schools and banks remained closed in the city center, although life began returning to normal in some outlying areas after President Laurent Gbagbo called late Wednesday for protesters – many of whom are thought to be his supporters – to leave the streets and go back to their jobs.

The latest bout of unrest began Monday in the government-held south after a U.N.-backed international mediation group recommended that parliament’s expired mandate not be renewed.

Gbagbo is leading a one-year unity government that has diminished his executive powers.